In numerous industries continuous sheets of material, commonly referred to as "webs," pass over rollers at relatively high speeds. A persistent web problem is the formation of cross-web wrinkles. Varying longitudinal tension, air resistance, operating vibrations, and other factors play roles in causing cross-web wrinkles. Materials particularly prone to wrinkling are paper, fabric, and plastic film. In the printing industry, web wrinkling is especially problematic when webs wrinkle before the ink dries.
There are several known techniques for removing web wrinkles which involve physically contacting and manipulating the web. Numerous compressible rubber rollers with various surface configurations have been developed, which are pressed against webs for wrinkle removal. Recently, pivoting rollers for tension equalization have been used to remove wrinkles, as illustrated by U.S. Pat. No. 5,727,753 invented by J. C. Harris, the inventor of this present invention.
Channeled Rollers: Web Contact Techniques
Also well known is the use of rollers which are channeled, fluted, or spiraled, to make contact with and to physically manipulate webs. Channeled rollers have been largely used to oil, wet, move, stretch, guide, or cut webs, or to crush webbed materials by means of physical contact between the channel lands and the web. (A channel land is an outward portion which is the inverse of the channel and adjacent to the channel).
Wrinkle Removal
Well known techniques for removing wrinkles with channeled rollers are disclosed in U.S. Pat. No. 3,828,998 [Gross] (helically bladed roller used to remove wrinkles in web through frictional contact between blades and web); U.S. Pat. No. 4,101,212 [Sumiyoshi] (channeled roller used to press an image transfer web onto a photosensitive plate and to remove any wrinkles in the web by means of frictional contact between channel lands and the web); and U.S. Pat. No. 4,276,911 [Pfarrwaller] (channeled roller used in a fabric take-off apparatus, to prevent the formation of folds by means of frictional contact between the channel lands and the fabric web).
Two techniques have specifically addressed the problem of wrinkle formation through web stretching, as disclosed in U.S. Pat. No. 4,566,162 [Brands] and U.S. Pat. No. 5,188,273 [Schmoock] (channeled rollers used to stretch webs and prevent wrinkle formation in webs by means of frictional contact between the channel lands and the web).
Liquid Applications
There are various liquid applications for channeled rollers, as disclosed in U.S. Pat. No. 579,141 [Dunn] (channeled roller used to oil and season hides and skins by means of collecting oil in roller channels and distributing oil onto hides and skins); U.S. Pat. No. 595,669 [Chadwick] (channeled roller used to oil skins for the preparation of leather by means of collecting oil in roller channels and distributing oil on skins); U.S. Pat. No. 4,465,544 [Fischer] (channeled roller used to redistribute paste as it builds up on a pasting roller, by means of frictional contact between the channel lands and the paste on the pasting cylinder); and U.S. Pat. No. 5,222,434 [Smith] (channeled roller used in printing press to collect ink in channels and feed ink through a printing press).
Crushing
Channeled rollers have also been used to crush various materials, as disclosed in U.S. Pat. No. 3,513,645 [Garrett] (two or more channeled rollers used to crush hay and other crops by means of pressing the web between two channeled rollers) and U.S. Pat. No. 4,242,409 [Parker] (two or more channeled rollers used to crush or crimp webs for reinforcing non-woven mats and giving mats flame retardation qualities).
Fabric Spreading
There are known techniques for using channeled rollers to separate and spread fabric, as disclosed in U.S. Pat. No. 1,457,276 [Isherwood] (channeled roller used to spread cloth in cloth handling machines by means of frictional contact between channel lands and cloth) and U.S. Pat. No. 2,717,037 [Goodwillie] (channeled roller used to separate relatively narrow webs, which originated from a single, larger web, by means of frictional contact between channel lands and the web).
Web Alignment
In addition, channeled rollers have been used to align webs, as disclosed in U.S. Pat. No. 2,176,835 [Cumfer] (channeled roller used to prevent web mis-tracking or slippage and to remove excess asphalt from web by means of frictional contact between channel lands and the web) and U.S. Pat. No. 4,832,186 [Conrad] (channeled roller used to maintain the alignment of webs over rollers by means of frictional contact between the channel lands and the web).
The diverse foregoing techniques all involve physical contact with a web in order to physically manipulate the web. These techniques have limited success when used with delicate webs or webs in printing and imaging applications. Physical manipulation of delicate webs is known to cause undesired web marking, micro-fractures, tears, and a general decrease in web tensile strength. In printing and imaging applications, the ink or images are smeared and damaged when the web is physically manipulated with a roller.
Channeled Rollers: Web Non-Contact Techniques
Channeled rollers have previously been used in manners other than for contacting a web and physically manipulating it. U.S. Pat. No. 3,405,884 [Patterson] discloses a channeled roller used to remove excess air from underneath a web in order to prevent web misalignment. The channel lands make physical contact with the web. The channels act as vents, enabling air to escape from between the roller and the web, to the ambient atmosphere.
The Patterson patent did not disclose a technique for removing web wrinkles. It disclosed a technique for air removal. Even if applied to the wrinkle problem, the technology disclosed in the Patterson patent could not be used to remove cross-web wrinkles without the channel lands physically contacting and manipulating the web.
In a different application, air bars have been used in web accumulators to maintain proper web tension, as disclosed in U.S. Pat. No. 5,775,623 [Long]. During web processing, there is often a need to isolate one web from another for a certain amount of time. Web accumulators are used for this purpose. The disclosed web accumulator involved two vertical, parallel plates having air bars mounted on their top edges. The vertical plates discharge pressurized air, forming a pressurizing chamber.
The web rests upon one air bar, recedes down into the chamber, and rests upon the other air bar. The air bars are smooth surfaced, porous bars which discharge pressurized air onto the web. The purpose of the air bars is to enable new web material to enter the chamber for accumulation, without damaging the web.
The air bars disclosed in the Long patent could not be used to remove cross-web wrinkles because the bars are not channeled. Consequently, the air discharged from the air bars only provides a radial force, not a force along the width of the web. With no forces being applied across the web width, cross-web wrinkles will not be removed.
In addition to the need for non-contact wrinkle removal, in numerous industries there is a need to treat webs during the manufacturing process through heating, cooling, moisturizing, drying, or otherwise treating webs through the application of particular gases. One known technique for heating and cooling webs is passing temperature regulated fluid through the center of a roller. The fluid heats or cools the roller, and as the web passes over the roller, the web is heated or cooled. Heating and cooling rollers in order to regulate web temperature is inefficient. The energy required for roller heating and cooling can be prohibitively expensive.
Known techniques for moisturizing and drying webs are nozzle spraying and using fans to blow mist onto the webs. These moisturizing techniques have the disadvantage of condensation formation, dripping, and non-uniform moisturization, all of which cause web weakening and tearing.
Furthermore, these known techniques do not offer a single system which successfully addresses web wrinkle removal and prevention, web heating and cooling, web drying and moisturization, removal of dust and debris from webs and rollers, and roller braking.
From all of the foregoing discussion, it is quite apparent that a significant need exists for a roller which addresses the recognized problems which have faced manufacturers of flexible materials and printed paper for so long without a viable solution.
Accordingly, an object of the present invention is to provide a roller which creates web tension for wrinkle removal and prevention by means of gas pressure.
Another object of the present invention is to provide a roller which heats and cools webs by means of relatively hot or cold gas pressure.
An additional object of the present invention is to provide a roller which drys or moisturizes webs by means of relatively dry or moist gas pressure.
Still another object of the present invention is to provide a roller which cleans webs and rollers by means of air suction pressure.
Yet another object of the present invention is to provide a roller which has a gas pressure-based braking system.